In isotope separation by isotopically selective photoexcitation of one isotope in an environment of plural isotopes, as for example discussed in commonly assigned U.S. Pat. No. 3,772,519, incorporated herein by reference, it is common to find a plurality of laser beams separately generated. It is desired to combine these into a composite beam having components from each of the separate laser beams. It is known that laser beams, or radiation in general, of differing frequencies in separate beams may be combined onto a single path having colinear superimposed beams composed of components of each of the original beams by the use of dichroic elements. Additionally, it is known as, for example, discussed in commonly assigned U.S. Pat. No. 3,924,937, that a plurality of laser beams of pulsed radiation having sequentially triggered pulses in each beam may be combined using a system of rotating optics.
For high power applications, the losses inherent in dichroic elements, particularly when combining laser beams of closely spaced frequency, will reduce the efficiency, or power available in the combined beams. Similarly, the use of rotating optics to provide beam combining in the case of time sequenced, pulsed beams while feasible, presents an element of mechanical complexity which it might be preferable to avoid.